As far as a video tape recorder (VTR) and a Digital Audio Tape (DAT) are concerned, a bulk type magnetic head 38 in FIG. 5 (a), a metal-in-gap type magnetic head 39 in FIG. 5 (b), and a laminate type magnetic head 40 in FIG. 5 (c) etc. are used. The bulk type magnetic head 38 shown in FIG. 5 (a) comprises at least a magnetic substance 42 such as ferrite, sendust, and permalloy which forms a magnetic path, a magnetic gap 41, and a non magnetic material 43 such as glass for fixing two cores of magnetic circuits 47, 48 which form the magnetic gap. The metal-in-gap type magnetic head 39 shown in FIG. 5 (b) comprises at least a high magnetic saturation substance 44 such as a metal film which forms a magnetic path in the vicinity of a magnetic gap, a magnetic substance 42 such as ferrite, sendust, permalloy etc. which forms the magnetic path besides the vicinity of the gap, a magnetic gap 41, and a non magnetic material 43. The laminate type magnetic head 40 shown in FIG. 5 (c) comprises at least a magnetic substance 45 forming a magnetic path, a magnetic gap 41, and a non magnetic material 46 such as ceramics for supporting the magnetic substance.
Conventionally, with regard to the bulk type magnetic head 38 and the laminate type magnetic head 40, a magnetic path was composed of magnetically equal materials (magnetic substances 42, 45) and initial permeability was also considered as being isotropic and equal. In case of the metal-in-gap type magnetic head 39, although the high magnetic saturation substance 44 such as a metal film which forms the gap part and the other part 42 of the magnetic substance have different initial permeability, each of the initial permeability was also considered as being isotropic and constant. However, a single crystal ferrite or a magnetic thin film generally has anisotropy in crystal, so that the initial permeability also differs according to the azimuth. Therefore, it can be anticipated that magnetic recording characteristics change in accordance to the azimuth. Furthermore, the non magnetic material 43 such as glass etc. is used for bonding two cores 47 and 48, and depending on the type of this non magnetic material 43, magnetic recording characteristics of the magnetic head 39 differed greatly. Probably, this was due to the fact that the magnetic characteristics of the magnetic material changed by thermal stress caused by the difference of thermal expansion coefficients between the non magnetic material 43 and the magnetic material 44 composing the magnetic path. However, since these phenomena are complicated and difficult to analyze, composite substances of a magnetic head were selected and the size of the head was designed on the basis of experiences.
A conventional method for analysis of magnetic characteristics will be explained in an example of a magnetic head as one of a typical magnetic devices.
Now, Maxwell's fundamental equations of electromagnetic field which rule the electromagnetic field are shown in the following equations 1 to 4 (Finite Element Method of Electrical Engineering, Autor: Takayoshi Nakada, Publisher: Morikita Shuppan, 1982). ##EQU1## In the above-noted equations, B represents a magnetic flux density, H represents a magnetic field strength, D represents a dielectric flux density, E represents field strength, J represents a current density, t represents time, and .rho. represents a charge density. A magnetic flux distribution and a magnetic field distribution comprising magnetic characteristics can be obtained by solving the equations 1 to 4 in combination under appropriate boundary conditions.
In a conventional method of analyzing magnetic characteristics of a magnetic device, the equations 1 to 4 are solved in combination under optional boundary conditions, for example, with a continuous magnetic flux, to obtain a magnetic flux distribution and a magnetic field distribution by forming magnetic flux continuously. By referring to a method of analyzing magnetic characteristics of a magnetic head by using the finite element method, a magnetic body comprising a magnetic path is divided into several elements, and these boundary conditions and material characteristics of each element and initial permeability .mu. or a curve of magnetic flux density--magnetic field strength (B--H curve) are input in an apparatus for analysis of magnetic characteristics. The conventional method for analysis of magnetic characteristics was conducted such that the magnetic characteristics such as the curve of magnetic flux density--magnetic field or the initial permeability defined as the equation 5 were measured in advance, and the measured data were provided at an input part of the apparatus for analysis of magnetic characteristics. ##EQU2##
On the other hand, the direction of an easy axis of a magnetic substance is determined by an angle formed with a magnetic field, and initial permeability changes depending upon this angle. In other words, when magnetic characteristics of a magnetic device are analyzed by using initial permeability, even if the initial permeability of each part change depending on the direction of a magnetic moment in each part of the magnetic device, the initial permeability were input in a conventional apparatus for analysis of magnetic records without taking the direction of the magnetic moment in each part into consideration.
Similarly, a curve of magnetic flux density--magnetic field strength also changes the optimum point of energy due to the direction of an external magnetic field, and a magnetic flux within a magnetic body changes the flowing direction. Therefore, when the flow of magnetic flux in the entire device is obtained by using the same curve of magnetic flux density--magnetic field strength and the equation 3 which shows the continuity of magnetic flux, the results obtained do not hold good for the actual state.
Furthermore, when a single crystal magnetic material or a magnetic thin film is used, initial permeability or a curve of magnetic flux density--magnetic field differ greatly according to the azimuth. In addition, the initial permeability or the curve of magnetic flux density--magnetic field also changes in accordance to internal stress possessed by the magnetic device. However, it was impossible to obtain the initial permeability or the curve of magnetic field--magnetic flux density for each azimuth of respective material or element composing the magnetic device.
Moreover, when a magnetic device is composed of a plurality of magnetic substances and non magnetic substances, and when each substance has different thermal and internal stress, it was hardly taken into consideration how the magnetic characteristics in each part or in the entire magnetic device changed.